Many types and mixtures of metal salts and soaps of natural or synthetic organic acids, particularly carboxylic acids, have been suggested and commercially offered over several decades. These have been used to supply metals in forms which are soluble in organic liquids, especially in various hydrocarbon oils and solvents, to form solutions having various desired properties and uses. For example such metal containing solutions may be useful as catalysts such as in fuels or in paints, varnishes and other film forming compositions. Many of these salts and soaps also have been useful as lubricant additives where high solvent solubility has not been of such importance.
Desire for economy in the production of such materials or for improved product quality has led to several variations in methods of producing the metal soap compounds by the classical double decomposition reaction and, as exemplified by Olson U.S. Pat. No. 2,753,049, by direct metal reaction.
As various organic carboxylic acids have become available in commercial quantities, either from new natural sources, or as synthetic acids or standardized synthetic acid mixtures, the possibility of using these to produce metallic salts or soaps has been motivated, for example, by a lower price; by a relative uniformity of the commercial acids; or by a better color, or at times the non-colored, characteristics of the salt products; by higher solubility of the salt products in various solvents in other components of ultimate products for which the metal salt is to be used; or stability in storage of the metal compositions or of their solutions. Prior art salt or soap compositions contain one mole of a carboxylate group per equivalent of metal present and they generally have a resinous, non-crystalline structure further characterized by a usual absence of any hydroxyl groups.
Other more complex metal organic compositions also have been investigated and marketed. Examples of the complex compositions are found in, for example, Rinse U.S. Pat. No. 3,518,287 or Collins et al U.S. Pat. No. 3,941,606.
High metal content with retention of high solubility has been sought, at times to minimize introduction of material other than catalytically active metal atoms, for example, into a process or product environment, to reduce raw material cost or to minimize weight or volume of the metal composition thereby reducing required storage space, packaging costs, or freight and other shipping costs.
Hence considerable attention has been given in the prior art to the production of the so-called overbased metal soaps or compositions, that is, compositions having greater than one-to-one ratios of metal-to-acid equivalents, for example, the Piotrowski et al U.S. Pat. Nos. 3,827,979 (by a carbonation process); Le Suer et al 3,312,618; Asseff et al 2,616,904; 2,616,905; Norman et al 2,595,790; Murphy 3,725,441; and patents cited in these. The preparation of oil-soluble metal soaps of various metals and acids and mixtures of acids, including some basic lead soaps is described in U.S. Pat. No. 2,584,041. Water is required in the process and the presence of air is optional.